The present invention relates to induction heating coils, and more particularly, to a single turn coil which provides heating for uniform sealing of lids to food containers around a complete circumference of the containers.
Plastic containers are commonly used for the packaging of food and for a wide variety of other items wherein a plastic lid is bonded to the container by the application of heat. One method of bonding involves the use of a laminated plastic lid having a layer of metal foil. A power supply provides an electrical current to a nearby induction coil which induces an electrical current into the metal foil to develop heat which melts portions of the lid and container and fuses the lid to the container. Multiple turn induction coils are rather bulky and difficult to mount in position to press the lid against the container during the sealing operation. Single turn coils are more convenient for pressing against the lid but have a small gap between the ends which causes a poor seal in an adjacent portion of the lid.